Outdoor stereo setup

Getting an in ground pool and screened in enclosure connected to my back porch. Wanting to add a stereo but not just an ipod dock. Any recommendations? Im thinking 4 Polk Audio Atrium8, or Definitive Technology AW 6500. What receiver would be recommended? Dont plan on having a tv so I guess all I need is 4 channel, iPod hookup, and radio. Budget is $1500.